Heretofore, there have been known syringes in which a needle is integrally fixed to a glass syringe barrel as a needle-equipped syringe. The needle should be securely fixed to a syringe nozzle in such needle-equipped syringes, however, it is not easy to keep a tightly closed condition between the needle and the glass syringe nozzle to be fixed thereto because of inferior compatibility between metal and glass.
Further, as dimensional accuracy of conventional needle-equipped glass syringe barrels is generally low, it is difficult to mass produce them stably. In a conventional method of glass syringe barrel production, a thin metal bar such as tungsten is temporarily set at a nozzle head to form a hole for needle during glass molding, which is removed to fix a needle after the syringe barrel is molded.
According to this method, however, metal (tungsten) might remain and stick in the syringe barrel and is to be washed off by an additional after treatment, or else an interaction of the metal with injection liquid would arose a problem of aggregation caused by an insoluble substance.
In order to avoid disadvantages as described above, a resin syringe barrel has also been produced by injection molding as shown, for example, in FIG. 8. According to such a conventional method, it is an essential process to fix a needle 82 to a nozzle 83 by means of an adhesive 84 to complete a syringe barrel 81, thereby inconveniently lowering the productivity. A ingredient of the adhesive might cause a problem of injection contamination.
There has been proposed another type of needle-equipped resin syringe barrel produced by injection molding for the purpose of resolving above mentioned inconvenience (see, for example, Japanese Patent A No. 9-66104 as a cited patent literature No. 1). In this case, the process of injection molding itself is advantageous to mass production, however, fixing strength of the needle to the syringe barrel should necessarily be guaranteed.
As is unclear from the patent literature No. 1, no novel technique has been known on a connecting structure of the needle and the syringe nozzle or a structure of mold, for example, a setting manner of the needle in the mold. That is to say, a technique to integrate the needle and the resin syringe barrel is quite poor at present.
Injection molding of needle-equipped syringe barrels using a synthetic resin is anticipated to be done in the following manner.
A core plate 930 is closed, followed by introduction of a needle carrying rod 94 provided with a needle 95 on a head thereof into a space formed by a cavity plate 910 as shown in FIG. 9(A). The needle 95 is then arranged in a needle holding hole H formed on a runner plate 920 and the carrying rod 94 is receded upward as shown in FIG. 9(B).
An inner mold 94 is inserted in the above mentioned space as shown in FIG. 9(C). In this situation, a cavity of a definite gap is formed between an outer surface of the inner mold 94 and a hollow wall surface of the cavity plate 910, which is not shown in the figure.
A resin is injected into the cavity as shown in FIG. 9(D) in which symbols M and r designate thus injected resin and a runner molded part as a runner product molded by a runner R, respectively. Then, the cavity plate 910 and a core plate 930 are opened to take out a syringe barrel 91 as shown in FIG. 10, while the runner product r is also taken out.